I see it as a testimony from kind of after life where the author who's seen the love of his life slowly getting away.
As his SO has left him, he's jumped from a bridge (for example) and deep in the water he realised that what he failed was to "truly look after her" and that's why she's left him.
Later, as his body's found and buried, from 6 feet under ground now he's doing what he should have done during his life.
I see it as a testimony from kind of after life where the author who's seen the love of his life slowly getting away.
As his SO has left him, he's jumped from a bridge (for example) and deep in the water he realised that what he failed was to "truly look after her" and that's why she's left him.
Later, as his body's found and buried, from 6 feet under ground now he's doing what he should have done during his life.